U.S. Pat. No. 4,468,400 describes tricyclic imidazo[1,2-a]pyridines with various ring systems fused to the imidazopyridine parent structure, which should be suitable for the treatment of peptic ulcers. —International Patent Application WO 95/27714 discloses certain substituted tricyclic imidazo[1,2-a]pyridines which are said to reversibly inhibit gastric acid secretion and to be useful in the prevention and treatment of gastrointestinal inflammatory diseases. International Patent Application WO 98/42707 discloses tetrahydroimidazo[1,2-h][1,7]naphthyridines which shall be suitable for the prevention and treatment of gastrointestinal diseases. WO 98/54188 describes fused dihydropyrans, which are said to be suitable for the treatment of peptic ulcer disorders. —In German Offenlegungsschrift 43 08 095, certain prodrug derivatives of pharmaceutically active agents with hydroxyl groups are disclosed.